A methodology for selecting the right seal material
Choosing an O-ring or seal elastomer is a process of elimination across four competing constraints: temperature, chemical/media resistance, mechanical duty and cost. This selector applies the first, second and fourth of those as hard filters, then ranks what survives so you can weigh the trade-offs quickly.
Step 1 — Define the temperature window
Start with the continuous-service temperature range the seal must survive, including any worst-case cold start and hot soak. A material only qualifies if its rated range fully covers your span. This single constraint often eliminates half the options — for example, standard FKM (Viton) is poor below about -26°C, while EPDM and silicone extend well into sub-zero territory.
Step 2 — Specify media resistance
Identify the primary fluids the seal will contact and require A- or B-grade resistance for each. Petroleum oils and fuels rule out EPDM, natural rubber and SBR; acids, bases, steam and weathering favour EPDM, FFKM or Aflas. Be honest about which categories are genuinely required — over-specifying resistance pushes you toward expensive perfluoroelastomers unnecessarily.
Step 3 — Set a cost ceiling and rank
Cost tiers run from $ (commodity NBR, EPDM) to $$$$$ (FFKM such as Kalrez). With a budget cap applied, the remaining candidates are ranked by how many requirements they satisfy at the top "Excellent" grade, then by lowest cost. The result is a shortlist — not a final answer. Confirm hardness, dynamic versus static duty and compression-set needs for your gland, and validate against real conditions. Send us your requirements and our engineers will recommend a specific compound.